The present invention generally relates to an acoustic transducer and, more particularly, to a microphone using the acoustic transducer.
Silicon-based condensers, which may be capable of converting acoustic energy to electrical energy, are also known as acoustic transducers. In some conventional acoustic transducer may include a perforated backplate and a membrane being susceptible to acoustic waves. For example, in microphones, a dielectric medium, such as air, may commonly exist between the backplate and the membrane so as to form a capacitor structure. Nevertheless, in certain aspects, the characteristics of a capacitor may largely depend on the spacing or distance between the backplate and the membrane. For example, the backplate and the membrane may need to be carefully arranged to avoid electrical contact that may result in short-circuiting. Accordingly, an extra isolation structure may even be used to prevent short-circuiting. A design that introduces one more backplate into an acoustic transducer may sense two differential potentials between each backplate and the membrane during vibration of the membrane. However, such an extra isolation structure or backplate may complicate the fabrication of acoustic transducers as well as raise the cost of production.
A conventional microphone may include at least one transducer and a housing covering the at least one transducer. Generally, the sensitivity of a microphone subject to acoustic waves may be determined by the supporting structure of the membrane, mechanical properties of the membrane and package type of the housing. For example, two inlets may be formed on a top surface of the housing of a conventional directional microphone, wherein the portion enclosing one of the inlets may include a damping material to delay an incident acoustic wave, thereby increasing sensitivity to acoustic waves from certain directions. Nonetheless, the process of fabricating a housing with different materials in such a design may be relatively complicated.
In another design, a conventional directional microphone array may include more than two omni-directional microphones to collect acoustic waves in all the directions from an acoustic source. However, the spatial characteristics of omni-microphones may limit downsizing of the directional microphone. For example, one of the spatial characteristics may require that omni-microphones in an array be designed with a spacing of 2×λ/π, which may be equivalent to approximately 0.64λ. Given an incident acoustic wave having a frequency of 20 Kilo Hertz (KHz), the spacing or distance between any two microphones in the array may be greater than 1 centimeter (cm), which may be oversized in view of the increasingly compact electronic products. Moreover, different sensitivities of the microphones in the array may result in inaccuracy during transduction.